Its not the leash or collar that you're using, your dog just doesn't have the confidence to walk in a place with entirely unfamiliar smells, sights and sounds.
Take slow steps with her, praise her and comfort her for going outside while on a leash. Give her five minutes outside and take her back in. (Do NOT pick her up unless she absolutely refuses to walk). Wait a few minutes and let her get relaxed and take her back outside.
All dogs have issues at first with a leash. My newest pup took a week of coaxing to get to walk on a leash and now he can't wait to go outside- he loves it.